The present invention is generally directed to electrical lighting devices and, more particularly, to an adjustable type lighting device where the illuminating portion is adapted to be manually repositioned to direct light to a variety of different positions and rotatable electrical connector units to be used in such an adjustable lighting device.
A variety of adjustable electrical lighting devices are known in the art. These devices are generally attached to and supported by a stationary surface and are adapted to allow the light emanating from the device to be directed to a variety of different positions and thereby regulate the light intensity on an object to be viewed by positioning the illuminating portion either closer or further away from the object. Commercially available electrical devices of this type generally include a plurality of arm members successively connected by swivel type joints, one end of the arm arrangement attached to a support surface and the other end to the illuminating or lamp portion of the device. Electric current is provided to the illuminating portion of the device by a pair of continuous electrical wires which pass through the arm arrangement or are closely associated therewith.
A significant problem in a device of this type is that after the device has been used for a period of time, the movement of the arms relative to each other during repositioning of the illuminating portion causes the continuous electrical wires to be repeatedly twisted and/or bent at the points where the arms are connected by the swivel joints. Such twisting and bending causes fatigue in the metal conducting portion of the electrical wires and may ultimately cause complete failure of the wires due to breakage of the metal conducting portion. Consequently, the lighting device is rendered inoperative and must be either repaired at considerable expense or discarded.
Examples of such lighting devices are shown in U.S. Pat. Nos. 2,389,340 to Bateman, 2,395,178 to Fiori, 2,820,885 to Neugass, 3,160,349 to Kent, 3,188,460 to Thorsen, et al, 3,213,273 to Zagel, 3,239,184 to Kirkeby and 3,970,835 to Crete. A characteristic of the devices disclosed in these patents is that the electrical wires connected to the illuminating portion of the devices are continuous and extend through the mechanical joints of the arms supporting the illuminating portion.
Also known in the art are axially rotatable or universal electrical connector units which do not have wires extending through the joint portion. These units may be used to conduct electrical current through a mechanical type joint without the possibility of electrical wire fatigue and consequent breakage of the wires. Examples of such units are illustrated in U.S. Pat. Nos. 913,831 to Low, et al, 958,448 to Vossberg, 2,259,999 to Bryant, et al, 2,652,546 to Christner, 2,519,933 to Rouault, 3,581,267 to Schreffler, 3,601,598 to Horn, 3,957,331 to Tantillo, et al and 3,963,291 to Maloof. These disclosed units are, however, generally cumbersome and would be difficult to manufacture on a large scale. In addition, these units are incapable of being held in a fixed position so as to be able to adequately support the weight of a lighting device in an extended position.